As it is known, to optimize the combustion process in an internal combustion engine with several cylinders, it is necessary for the air-fuel ratio in each cylinder to be in proximity to the stoichiometric value. The devices and methods currently utilized and available in the market are based on oxygen sensors, usually housed in the exhaust conduit in proximity to the catalytic converter.
However, these sensors present certain drawbacks, for example, they are subject to breakage. Furthermore, it is not normally possible to determine the air-fuel ratio of the single cylinders as the sensor signal refers to the exhaust gases from the single cylinders when already mixed in the exhaust manifold. The complicated signal treatments which would serve to reconstruct the air-fuel ratio of the single cylinders do not guarantee the precision necessary for the controller device which is supposed to realign the cylinders.